NORTHERN SPECIES OF ORCA. 171 



a complete covering of enamel to their free portion. Thus, it is, properly speaking, only a very 

 small piece, soon worn off, that deserves the name of crovirn in the part of the cachalot's tooth 

 standing out of the gum, and all the rest of it may be called a projecting part of the fang ; but 

 siich is not the case with the teeth of the Orcas. In these a constricted part, the neck, encom- 

 passed by the gum may be perceived between the crown and the fang, at least, in the teeth of 

 young individuals; the crown is gradually worn off as the animal gets older, but the fang, 

 though in the full-grown tooth, at least one and a half time longer than the crown, never grows 

 out to repair the loss, which may be supposed to take place in the cachalots, as we know from 

 our own observation that it happens in the beluga even to an extraordinary degree. 



The killers have thirteen to fourteen teeth on either side of both jaws ; the foremost of 

 those in the upper jaw is placed in the intermaxillary bone, and, as is the corresponding one 

 in the lower jaw, very near to the mesial line ; both are very small (3'" long, I'" thick) and 

 soon closed at the point of the root. In my two youngest skeletons (that of Mr. Thomsen, and 

 the one from the Faroe Islands), they were still hidden in the gum ; in all the old ones they 

 had, on the contrary, fallen out. The foremost tooth in the maxillary bone is also com- 

 paratively small (scarcely I'" long, 4'" broad towards the point of the root), and the three 

 hindmost ones are so short that they hardly meet the opposite ones, when the mouth is 

 closed ; but the eight middle maxillary teeth are almost equally long and strong. They are 

 somewhat more curved in the upper than in the lower jaw. Beneath the neck the root is per- 

 ceptibly enlarged, so that the thickest portion of the whole tooth is the superior half of the root, 

 and its conical form does not appear till in its inferior half towards the point of the root. In the 

 teeth of these two younger Orca skeletons, as well as in those of one of the separate crania from 

 the Faroe Islands, this conical portion of the root, however, has not yet been formed, and, 

 accordingly, all these teeth have still the form of a single cone, with all the modifications men- 

 tioned above ; bent as a hook towards the point, a little compressed, and with traces of a con- 

 striction in the middle most perceptible in the convex margin. 



But while having this their earliest form of a single cone almost an inch and a half high, half 

 an inch or one inch broad, the Orca teeth are not only still open teeth, but filled with the pulp to such 

 a degree that their sohd walls, though consisting of two layers of different kinds — in the crown 

 of dentine and enamel, in the root of dentine and cement — have scarcely anywhere a thickness 

 of more than half a line, not even at the very top of the crown, while the diameter of the hollow of 

 the pulp is about an inch. Like teeth in general, they present, at a very early period, when 

 removed from their natural places, a certain resemblance to small caps of paper, and are, of 

 course, extremely brittle. Such I have found them, not only in the two younger Orca crania 

 of the museum (that of Mr. Thomsen, and the smallest from the Faroe Islands, which is thirty- 

 two inches long), but also in the second from the same locality that is three inches longer. It is 

 not till in the third from the Faroe Islands whose length is forty inches, that the formation of 

 the dentine is almost finished in all the teeth, the two or three hindmost excepted. When sawn 

 through, a narrow elongated cavity alone remains for the pulp, whereas the remainder of the 

 tooth consists interiorly of dentine arranged in several concentric layers. 



In the teeth of the cachalots the formation of the dentine proceeds so very fast, that even 

 when quite small they have already very thick walls, presenting only a very small cavity for the 

 pulp at the point of the root in the shape of a very low cone. But, as we have seen, the contrary 

 is the case with the teeth of the Orcas, characterised by a surprisingly slow ossification, a 



